MC145026

•MC145027•MC145028•SC41343•SC41344

MOTOROLA

9

R1, C1

Resistor 1, Capacitor 1 (Pins 6, 7)

As shown in Figures 2 and 3, these pins accept a resistor

and capacitor that are used to determine whether a narrow

pulse or wide pulse has been received. The time constant

R1 x C1 should be set to 1.72 encoder clock periods:

R1 C1 = 3.95 RTC CTC

R2/C2

Resistor 2/Capacitor 2 (Pin 10)

As shown in Figures 2 and 3, this pin accepts a resistor and

capacitor that are used to detect both the end of a received

word and the end of a transmission. The time constant R2 x

C2 should be 33.5 encoder clock periods (four data periods

per Figure 11): R2 C2 = 77 RTC CTC. This time constant is

used to determine whether the Din pin has remained low for

four data periods (end of transmission). A separate on–chip

comparator looks at the voltage–equivalent two data periods

(0.4 R2 C2) to detect the dead time between received words

within a transmission.

VT

Valid Transmission Output (Pin 11)

This valid transmission output goes high after the second

word of an encoding sequence when the following conditions

are satisfied:

1. the received addresses of both words match the local de-

coder address, and

2. the received data bits of both words match.

VT remains high until either a mismatch is received or no

input signal is received for four data periods.

VSS

Negative Power Supply (Pin 8)

The most–negative supply potential. This pin is usually

ground.

VDD

Positive Power Supply (Pin 16)

The most–positive power supply pin.